Objectives:To determine hemodynamic response to amrinone in patients after cardiac surgery, in relation to the postoperative cardiac function, which was indicated by the required doses of catecholamines.Design:Prospective clinical study.Setting:Surgical intensive care unit in a university hospital.Patients:Fourteen patients who required a low-to-moderate dose of dopamine and dobutamine (group L) and 14 patients who required a high dose of dopamine and dobutamine (group H) after cardiac valve replacement.Interventions:A loading dose of amrinone (0.75 mg/kg) was administered during a 15-min period and the continuous infusion was followed incrementally by doses of 5, 10, and 20 μg/kg/min every 60 mins on the first postoperative day.Measurements and Main Results:Hemodynamic variables were determined by the radial and pulmonary artery catheters at a dose of 0, 5, 10, and 20 μg/kg/min. Two-way repeated-measures analysis of variance showed significant interaction in the two groups in cardiac index and mean systemic arterial pressure. Cardiac index increased in a dose-dependent manner in group L but was unchanged in group H. Systemic vascular resistance index decreased in a dose-dependent manner in both groups. The mean systemic arterial pressure decreased in group L at a dose of 5 μg/kg/min and returned to the baseline level at doses of 10 and 20 μg/kg/min. On the other hand, the mean systemic arterial pressure significantly decreased in group H at a dose of 20 μg/kg/min.Conclusions:The inotropic effects of amrinone after cardiac valve replacement may be associated with the postoperative myocardial reserve, which was indicated by the required doses of catecholamines, although a similar vasodilative effect was observed in both groups.